U.S. officials in Washington say they think Taliban fighters shot down a transport helicopter that crashed in Afghanistan, killing 38 people in the deadliest single incident for foreign troops in a decade of war there.

Those killed include 30 U.S. soldiers, most of them special forces, along with seven Afghan commandos and a civilian interpreter.

The Taliban has claimed it shot down the Chinook helicopter with a rocket propelled grenade late on August 5 in the central Afghan province of Maidan Wardak, just west of Kabul.

The Pentagon and the NATO-led International Security Assistance Force (ISAF) in Afghanistan say they are still investigating the cause of the crash.

One U.S. official said the dead included members of the Navy SEAL unit that killed Osama Bin Laden in early May, but were "unlikely" to be the same personnel.

U.S. President Barack Obama issued a statement paying tribute to the Americans and Afghans who died in the crash.